/*
 * handle transition of Linux booting another kernel
 * Copyright (C) 2002-2005 Eric Biederman  <ebiederm@xmission.com>
 *
 * This source code is licensed under the GNU General Public License,
 * Version 2.  See the file COPYING for more details.
 */

#include <linux/mm.h>
#include <linux/kexec.h>
#include <linux/string.h>
#include <linux/gfp.h>
#include <linux/reboot.h>
#include <linux/numa.h>
#include <linux/ftrace.h>
#include <linux/io.h>
#include <linux/suspend.h>

#include <asm/init.h>
#include <asm/pgtable.h>
#include <asm/tlbflush.h>
#include <asm/mmu_context.h>
#include <asm/debugreg.h>

static void free_transition_pgtable(struct kimage *image)
{
        free_page((unsigned long)image->arch.pud);
        free_page((unsigned long)image->arch.pmd);
        free_page((unsigned long)image->arch.pte);
}

static int init_transition_pgtable(struct kimage *image, pgd_t *pgd)
{
        pud_t *pud;
        pmd_t *pmd;
        pte_t *pte;
        unsigned long vaddr, paddr;
        int result = -ENOMEM;

        vaddr = (unsigned long)relocate_kernel;
        paddr = __pa(page_address(image->control_code_page)+PAGE_SIZE);
        pgd += pgd_index(vaddr);
        if (!pgd_present(*pgd)) {
                pud = (pud_t *)get_zeroed_page(GFP_KERNEL);
                if (!pud)
                        goto err;
                image->arch.pud = pud;
                set_pgd(pgd, __pgd(__pa(pud) | _KERNPG_TABLE));
        }
        pud = pud_offset(pgd, vaddr);
        if (!pud_present(*pud)) {
                pmd = (pmd_t *)get_zeroed_page(GFP_KERNEL);
                if (!pmd)
                        goto err;
                image->arch.pmd = pmd;
                set_pud(pud, __pud(__pa(pmd) | _KERNPG_TABLE));
        }
        pmd = pmd_offset(pud, vaddr);
        if (!pmd_present(*pmd)) {
                pte = (pte_t *)get_zeroed_page(GFP_KERNEL);
                if (!pte)
                        goto err;
                image->arch.pte = pte;
                set_pmd(pmd, __pmd(__pa(pte) | _KERNPG_TABLE));
        }
        pte = pte_offset_kernel(pmd, vaddr);
        set_pte(pte, pfn_pte(paddr >> PAGE_SHIFT, PAGE_KERNEL_EXEC));
        return 0;
err:
        free_transition_pgtable(image);
        return result;
}

static void *alloc_pgt_page(void *data)
{
        struct kimage *image = (struct kimage *)data;
        struct page *page;
        void *p = NULL;

        page = kimage_alloc_control_pages(image, 0);
        if (page) {
                p = page_address(page);
                clear_page(p);
        }

        return p;
}

static int init_pgtable(struct kimage *image, unsigned long start_pgtable)
{
        struct x86_mapping_info info = {
                .alloc_pgt_page = alloc_pgt_page,
                .context        = image,
                .pmd_flag       = __PAGE_KERNEL_LARGE_EXEC,
        };
        unsigned long mstart, mend;
        pgd_t *level4p;
        int result;
        int i;

        level4p = (pgd_t *)__va(start_pgtable);
        clear_page(level4p);
        for (i = 0; i < nr_pfn_mapped; i++) {
                mstart = pfn_mapped[i].start << PAGE_SHIFT;
                mend   = pfn_mapped[i].end << PAGE_SHIFT;

                result = kernel_ident_mapping_init(&info,
                                                 level4p, mstart, mend);
                if (result)
                        return result;
        }

        /*
         * segments's mem ranges could be outside 0 ~ max_pfn,
         * for example when jump back to original kernel from kexeced kernel.
         * or first kernel is booted with user mem map, and second kernel
         * could be loaded out of that range.
         */
        for (i = 0; i < image->nr_segments; i++) {
                mstart = image->segment[i].mem;
                mend   = mstart + image->segment[i].memsz;

                result = kernel_ident_mapping_init(&info,
                                                 level4p, mstart, mend);

                if (result)
                        return result;
        }

        return init_transition_pgtable(image, level4p);
}

static void set_idt(void *newidt, u16 limit)
{
        struct desc_ptr curidt;

        /* x86-64 supports unaliged loads & stores */
        curidt.size    = limit;
        curidt.address = (unsigned long)newidt;

        __asm__ __volatile__ (
                "lidtq %0\n"
                : : "m" (curidt)
                );
};


static void set_gdt(void *newgdt, u16 limit)
{
        struct desc_ptr curgdt;

        /* x86-64 supports unaligned loads & stores */
        curgdt.size    = limit;
        curgdt.address = (unsigned long)newgdt;

        __asm__ __volatile__ (
                "lgdtq %0\n"
                : : "m" (curgdt)
                );
};

static void load_segments(void)
{
        __asm__ __volatile__ (
                "\tmovl %0,%%ds\n"
                "\tmovl %0,%%es\n"
                "\tmovl %0,%%ss\n"
                "\tmovl %0,%%fs\n"
                "\tmovl %0,%%gs\n"
                : : "a" (__KERNEL_DS) : "memory"
                );
}

int machine_kexec_prepare(struct kimage *image)
{
        unsigned long start_pgtable;
        int result;

        /* Calculate the offsets */
        start_pgtable = page_to_pfn(image->control_code_page) << PAGE_SHIFT;

        /* Setup the identity mapped 64bit page table */
        result = init_pgtable(image, start_pgtable);
        if (result)
                return result;

        return 0;
}

void machine_kexec_cleanup(struct kimage *image)
{
        free_transition_pgtable(image);
}

/*
 * Do not allocate memory (or fail in any way) in machine_kexec().
 * We are past the point of no return, committed to rebooting now.
 */
void machine_kexec(struct kimage *image)
{
        unsigned long page_list[PAGES_NR];
        void *control_page;
        int save_ftrace_enabled;

#ifdef CONFIG_KEXEC_JUMP
        if (image->preserve_context)
                save_processor_state();
#endif

        save_ftrace_enabled = __ftrace_enabled_save();

        /* Interrupts aren't acceptable while we reboot */
        local_irq_disable();
        hw_breakpoint_disable();

        if (image->preserve_context) {
#ifdef CONFIG_X86_IO_APIC
                /*
                 * We need to put APICs in legacy mode so that we can
                 * get timer interrupts in second kernel. kexec/kdump
                 * paths already have calls to disable_IO_APIC() in
                 * one form or other. kexec jump path also need
                 * one.
                 */
                disable_IO_APIC();
#endif
        }

        control_page = page_address(image->control_code_page) + PAGE_SIZE;
        memcpy(control_page, relocate_kernel, KEXEC_CONTROL_CODE_MAX_SIZE);

        page_list[PA_CONTROL_PAGE] = virt_to_phys(control_page);
        page_list[VA_CONTROL_PAGE] = (unsigned long)control_page;
        page_list[PA_TABLE_PAGE] =
          (unsigned long)__pa(page_address(image->control_code_page));

        if (image->type == KEXEC_TYPE_DEFAULT)
                page_list[PA_SWAP_PAGE] = (page_to_pfn(image->swap_page)
                                                << PAGE_SHIFT);

        /*
         * The segment registers are funny things, they have both a
         * visible and an invisible part.  Whenever the visible part is
         * set to a specific selector, the invisible part is loaded
         * with from a table in memory.  At no other time is the
         * descriptor table in memory accessed.
         *
         * I take advantage of this here by force loading the
         * segments, before I zap the gdt with an invalid value.
         */
        load_segments();
        /*
         * The gdt & idt are now invalid.
         * If you want to load them you must set up your own idt & gdt.
         */
        set_gdt(phys_to_virt(0), 0);
        set_idt(phys_to_virt(0), 0);

        /* now call it */
        image->start = relocate_kernel((unsigned long)image->head,
                                       (unsigned long)page_list,
                                       image->start,
                                       image->preserve_context);

#ifdef CONFIG_KEXEC_JUMP
        if (image->preserve_context)
                restore_processor_state();
#endif

        __ftrace_enabled_restore(save_ftrace_enabled);
}

void arch_crash_save_vmcoreinfo(void)
{
        VMCOREINFO_SYMBOL(phys_base);
        VMCOREINFO_SYMBOL(init_level4_pgt);

#ifdef CONFIG_NUMA
        VMCOREINFO_SYMBOL(node_data);
        VMCOREINFO_LENGTH(node_data, MAX_NUMNODES);
#endif
}